Using encoding/json (TextMarshalJSON) in Go

Posted by GoDoc
Public (Editable by Users)

Package json implements encoding and decoding of JSON as defined in RFC 7159. The mapping between JSON and Go values is described in the documentation for the Marshal and Unmarshal functions.

Go
Edit 
package main

import (
	"encoding/json"
	"fmt"
	"log"
	"strings"
)

type Size int

const (
	Unrecognized Size = iota
	Small
	Large
)

func (s *Size) UnmarshalText(text []byte) error {
	switch strings.ToLower(string(text)) {
	default:
		*s = Unrecognized
	case "small":
		*s = Small
	case "large":
		*s = Large
	}
	return nil
}

func (s Size) MarshalText() ([]byte, error) {
	var name string
	switch s {
	default:
		name = "unrecognized"
	case Small:
		name = "small"
	case Large:
		name = "large"
	}
	return []byte(name), nil
}

func main() {
	blob := `["small","regular","large","unrecognized","small","normal","small","large"]`
	var inventory []Size
	if err := json.Unmarshal([]byte(blob), &inventory); err != nil {
		log.Fatal(err)
	}

	counts := make(map[Size]int)
	for _, size := range inventory {
		counts[size] += 1
	}

	fmt.Printf("Inventory Counts:\n* Small:        %d\n* Large:        %d\n* Unrecognized: %d\n",
		counts[Small], counts[Large], counts[Unrecognized])

}